3. Who first saw cells?

In the 1600’s

• England : Robert Hooke saw cells in cork.
• Holland: Anton van Leeuwenhoek saw cells in blood, sperm, rainwater
• Scientists of the 1600’s did not think these "cells" were important.

4. Why are most cells small?

• -Cells need to take in lots of nutrients and expel wastes. 
• -Plasma membrane acts to regulate this
• -Small cells have more surface area relative to volume.  This enables them to move materials in and out more quickly.

5. What are the two basic cell types?

6. Parts of the cell (structure & function) Fig. 2.3

Look at some cell parts by going to this site and clicking on models of a plant, animal and bacterial cell.  www.cellsalive.com/cells/3dcell.htm

Different cell parts perform different functions

a. Cell wall (fig. 1.9f and 2.4)

• Function: rigidity in plants
• Structure: cellulose

b. Plasma membrane (fig. 2.5)

• Function: regulates what passes into and out of the cell
• Structure: lipids act as a barrier and proteins act as doors to allow certain molecules to enter and exit the cell

c. Nucleus (fig. 2.3)

• Function: Contains the material of heredity (genes) which control how the cell functions. The nucleus is the control center of the cell.
• Structure: DNA surrounded by a membrane.

d. Amyloplast (fig. 2.7)

Function: Starch storage. For example, pea cells and potato cells are filled with amyloplasts.

e. Vacuole (fig. 2.3)

Function: Toxic waste dump. Plants do not have an excretory system so they must isolate toxins. For example, plants that grow well in salt water are able to do this by concentrating lots of salt in their vacuoles.

f. Chloroplasts (fig. 2.3 and 2.6)

• Function: Carry out photosynthesis
• Structure: Membranes surround chlorophyll and proteins

g. Mitochondria (fig. 2.3)

• Function: Powerhouse of the cell. Produces ATP. Carries out cellular respiration.
• Structure: Membranes surround proteins

7. How did chloroplasts and mitochondria arise? (box 2.1 p. 25)

Observations

Chloroplasts and mitochondria are:

• Self-replicating
• Contain their own DNA
• Size of prokaryotic cells
• Have 2 membranes surrounding them

Endosymbiosis theory: this evidence suggests that chloroplasts and mitochondria were once free-living prokaryotes swallowed up by another cell. Rather than being digested, they developed a mutually beneficial relationship (symbiosis).

8. Structure-function relationship at the cellular level

Even though there are 2 basic cell types (prokaryotic and eukaryotic), there is still a tremendous diversity among cells. For example, over 200 kinds of cell types are found in humans. Plants also have many types of cells. Both cell shape and the number and types of structures inside the cell are related to its function.

Examples:

• Nerve cells in humans are long and skinny and act as conductors of nerve impulses.
• Guard cells in plants are kidney shaped and filled with chloroplasts. They function as gates to open and close stomata.

Cell Comparison

Exercise:

    Look at the leaf on p. 43, fig. 3.11.  How many kinds of cells can you find?  What does each cell type do?

In humans, there are over 200 separate kinds of cells (all eukaryotic cells) while in plants, there are probably about 20 different kinds (again all eukaryotic).

Leaf Cell Example:  How would a cell in a tea leaf function?

Think of a cell as being a factory manufacturing products.  A tea leaf (genus Camellia) is making caffeine.  Fill in the blanks to describe how this process occurs.

1.      The information on how to make caffeine is found in the structure called the

______________ which contains the molecule called ______________.

2.      The information of DNA is used by the cell to build proteins.  Many of the proteins are enzymes.  Enzymes control ____________________________.

3.      After the correct enzymes are built by the DNA and caffeine is manufactured, it is stored in the _______________, the storage structure of the cell.  Caffeine is a stimulant of the central nervous system and deters _________________from eating the plant.

4.      The energy to build caffeine comes directly from a molecule called ATP.  ATP is like the electricity that cells run on.  ATP is made in the power plant of the cell called the ________________________.  This structure uses a sugar called glucose as its main fuel.

5.      Animals get glucose from their diet.  A tea plant manufactures glucose in a process called ______________which takes place in the leaf.   A structure in the leaf where this process takes place is called the ____________ . In the roots, this glucose is stored as starch (long chains of thousands of glucose units) in structures called ___________.

6.      The energy the tea plant uses for photosynthesis comes from ___________.

7.      Oxygen is a waste product of photosynthesis.  It moves out of the tea cell across a barrier called the _________________.

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